United doesn't care. Their baggage handling contractor (usually sats/dnata) would sweep up the bags after some time and put them in the unclaimed area. You will go there to reclaim your bag
that saying, have you looked at yotelair at publicside jewel? It's pretty cheap too
scoot allows early check-in anyways. As long as u have the appropriate visa and timing looks right, you can enter Singapore, pick up bags, early check-in, visit jewel , then enter airside again. Note that you can enter/exit immigration only once per leg, cannot do it twice on one leg
scoot
From 3 hrs to 18 hrs before departure Available from 0430hrs to 0130hrs at T2 Row 11 and 0600hrs to 2359hrs at Jewel ECI Lounge
Early Check-in | Changi Airport Singapore